It will be recalled from our previous application that bedding for waterbeds has presented problems for the waterbed user since the use of waterbeds has become popular. Waterbed mattresses are like bladders that contain water. When weight is placed on the bladder or mattress at one location the water has a tendency to surge outwardly from that location towards the extremities of the bladder or mattress causing the extremities to swell to the extent of its elasticity. This is particularly true around the mattress or bladder corners. Even baffled mattresses or bladders are effected. The result is that the corners of the mattress cover and sheets are forced off of the mattress by the surge effect. Since a surge takes place every time one gets in bed, the result is loose bedding while sleeping and an every morning task of totally remaking the bed.
In addition to the foregoing problem, the mattress will have a tendency to surge just from the making of the bed making it at least frustrating if not impossible to fit the bedclothes back around the mattress corners. Many a bed maker has in time just purchased larger bedclothing and jammed it down between the mattress and the side, head and footboards in an attempt to solve this problem. Such a solution is usually a failure and leads to very uncomfortable sleeping conditions on wadded up sheets and mattress covers.
Various solutions have been attempted in the form of regular or fitted bedclothing for waterbed mattresses. One such attempt has involved the joining of the bedclothing near the foot end of the bed such that the top sheet is sewed to the bottom sheet or both top and bottom sheet are joined near the foot end of the bed to the mattress cover. Such solution has a tendency to result in the restless sleeper tearing or ripping the sheets while sleeping. In addition, the real result is simply to reduce the number of corners to be dealt with, but the problem still remains for the remaining corners.
Another solution that has been tried is to make bedclothing corners which are large enough to accommodate the surge. That solution results in bedclothing that does not fit well and comes loose for that reason. It also causes wadding and uncomfortable creasing of the bedclothes.
A variation on the foregoing scheme was to make the corners from an elastic material in an effort to accommodate the surge. This increases the cost of the materials and the cost of labor to produce the bedclothing and in addition does not solve the problem as a result of the limitations on the elasticity of the material.
Various means have been tried to fasten the bedclothing to the side, head and footboards of the bed with a variety of bad results including ripping, tearing and difficulty in making the bed. There has even been an attempt to solve the problem by having the bedclothing circumscribe the mattress in whole or via elastic straps which is extremely cumbersome in making the bed and changing the bedclothing especially when the weight of a waterbed mattress is taken into consideration.
The proposed solution of our prior application works very well on substantially fully filled, firm mattresses. However, some users of waterbeds prefer a mattress that is not substantially fully filled and firm. On such mattresses the user discovers that pressure in the central area of the mattress downwardly, as from human weight, causes the mattress margins to turn upwardly giving the mattress a concave appearance. On generally rectangular mattresses, the corners of the mattress experience a short term temporary reduction in water allowing the mattress corner to withdraw from the sheet or mattress cover opening them to come upward within the sheet or cover pulling the sheet or cover with it all along the mattress margins between the corners. This is because the surge will affect the side margins of a generally rectangular in plan view waterbed mattress, which is by far the most common variety.